Wastewater treatment

ABSTRACT

A system and method for treating wastewater by continuously flowing wastewater into a chemostat and continuously discharging clean water out of the chemostat. The system can include sensors and an electronic controller for on-line measuring ambient parameters in the chemostat and adjusting the chemostat&#39;s operating conditions accordingly.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/155,811 filed on Jun. 10, 2008, now U.S. Pat. No. 8,038,881, whichclaims the benefit of priority of U.S. Provisional Patent ApplicationNo. 60/929,070 filed on Jun. 12, 2007. The contents of all of the aboveapplications are incorporated by reference as if fully set forth herein.

FIELD OF THE INVENTION

This invention relates generally to industrial wastewater treatment andmore specifically to a system and method for controlled wastewatertreatment using a chemostat.

BACKGROUND OF THE INVENTION

Industrial wastewater is produced as a by-product of industrialprocesses, for example, processes in oil refineries and petrochemicalplants.

Wastewater from refineries may be highly contaminated given the numberof sources it can come into contact with during the refinery process.This contaminated water may, for example, be process wastewater fromdesalting, water from cooling towers, storm water, distillation, orcracking. This water can be recycled through many stages during therefining process and typically goes through several treatment processes,including wastewater treatment, before being released into surfacewater.

Existing technologies for the treatment of contaminated water in oilrefineries and petrochemical plants consist of a series of sequentialsteps, including the steps shown in the flow diagram of FIG. 1.

To-date, the majority of the wastewater treatment is done by using the“activated sludge” (depicted in the flow diagram of FIG. 2) or “membranebioreactors” (“MBR”) (depicted in the flow diagram of FIG. 3)technologies. In general, in activated sludge plants, atmospheric air orpure oxygen is bubbled through wastewater combined with organisms, todevelop a biological floc which reduces the organic content of thewastewater. In all activated sludge plants, once the industrialwastewater has received sufficient treatment, an additional step ofsettling out the biological floc is required. Part of the settledmaterial, the sludge, is returned to the system to re-seed the newindustrial wastewater entering the tank. The remaining sludge then needsto be disposed of. The MBR technology combines the use of an activatedsludge bioreactor with a cross flow membrane filtration loop. Themembrane is used for the additional step of biological floc removal, byfiltration, and as a result recycled and waste sludge are produced.

U.S. Pat. No. 6,916,427 to Roth discloses a method of purifyingwastewater, including running the wastewater as a fluent into aheadworks where some preliminary treatment takes place, passing thefluent into a primary reservoir where it is analyzed as to certaincontrol parameters such as pH, dissolved oxygen and/or dissolved solids.Thereafter the fluent flows into a primary reactor having a plurality ofelectrolytic cells therein. While in that reactor the fluent issubjected to electrical contacts which are located at the bottom and thetop of the reactor. The effluent from the primary reactor passes througha ratio weir into a secondary receptor containing sensors for themeasurement of control parameters such as pH, DO, TDS and chlorine.Thereafter, the fluent is passed to a filtering device.

U.S. Pat. No. 5,989,428 to Goronszy provides a method and apparatus fortreating waste material to remove selected components form the waste isdescribed using a reactor or a series of reactors in fluid communicationwith each other for receiving the waste to be treated as influent. Theinfluent forms a biomass including the waste and microorganisms and istreated by controlling the metabolic activity of the microorganisms bymonitoring the oxygen utilization rate or the potential oxygenutilization rate of the biomass so as to determine the required amountof oxygen to be supplied to the biomass and to determine the period ofaeration of the biomass in order to maintain a predetermined oxygenutilization rate or value so as to remove the selected components of thewaste. The preferred selected components to be removed are nitrogenous,carbonaceous and/or biological phosphorus containing materials orderivatives.

US Published Patent Application No. 20080047903 to Morse discloses asystem and process for optimizing chemical additions, mixing energy,mixing time, and other variables while treating a contaminated liquidstream. Samples from the contaminated liquid stream are tested todetermine the optimal parameter for each variable, including type andamount of the chemicals to be added, chemical sequence, mixing energy,mixing time, temperature, and pressurization. A system of mixers, aflotation chamber, and a dewatering subsystem are designed to achieveoptimal turbidity of the wastewater stream. The system can be modifiedin real-time in response to a continually changing contaminated liquidstream via a controller and set of sensors, valves, and ports. Theprocess takes place during the pre-treatment stage. There is need for astable, efficient, continuous and cost-effective wastewater treatmentprocess to overcome the shortcomings of existing processes.

SUMMARY OF THE INVENTION

Disadvantages of existing wastewater treatment processes have been foundto include:

1. An additional step of biological floc removal by sedimentation orfiltration is required, since the TSS (total suspended solids) in theeffluent of these processes is about 2,000 ppm in the activated sludgebioreactor and about 4,000 ppm in the MBR bioreactor, thus much higherthan the usually required 1-50 ppm.2. Waste sludge is produced and needs to be disposed of.3. Sludge is recycled to the process and as a result, the biologicalprocess is done in a very high cell density (bacterial concentration),which may lead to reduction in the carbon and nitrogen consumption. Inactivated sludge and MBR the retention time of a bacterium in thebioreactor is days-weeks

During a biological treatment bacteria consume the carbon source (e.g.oil) and convert it to: CO2 and material for cell growth (morebacteria). Therefore, to get efficient carbon degradation, bacteriashould be in the log phase which is marked by rapid exponential growth(more new bacteria produced).

The log phase of bacterial growth is followed by the stationary phase,in which the size of a population of bacteria remains constant andmetabolic activity is drastically reduced. If incubation continues afterthe population reaches the stationary phase, a death phase follows, inwhich the viable cell population declines.

Recognizing the basic bacterial growth cycle clearly suggests thatworking at high cell densities, as routinely carried out in “activatedsludge” and “MBR,” may lead bacteria to a stationary phase. Tosummarize, working in a high cell density leads to a decrease inmetabolic activity and eventually to a decline in the viable cellpopulation and, therefore, to a decrease in carbon and nitrogenconsumption. FIG. 4 illustrates a graph depicting the bacterial growthcycle described above.

“Activated Sludge” and “MBR” are complicated processes, with multiplesteps and high maintenance requirements. For example, in the “MBR”process membrane fouling is the most serious problem affecting systemperformance. Frequent membrane cleaning and replacement is thereforerequired, significantly increasing the operating costs. Different typesof chemical cleaning are recommended: chemically enhanced backwash(daily); maintenance cleaning with higher chemical concentration(weekly); intensive chemical cleaning (once or twice a year).

Described herein are systems and methods for treating wastewater bycontinuously flowing wastewater into a chemostat and continuouslydischarging clean water out of the chemostat. The described methodsalleviate many of the disadvantages associated with prior art watertreatment systems.

One embodiment is a wastewater treatment system including a chemostatincluding a wastewater input, a clean water output, a bacteria input, anutrients input, an oxygen input and sensors for measuring ambientparameters. The system also includes an electronic controller connectedwith the sensors, the controller configured to receive measurements fromthe sensors and control operating conditions of the chemostataccordingly. The electronic controller is configured to maintain a lowenough concentration of bacteria within the chemostat to be dischargedto the nature without further treatment.

The controller may control at least one of the waste water input, thenutrients input, and the oxygen input. The system may be configured sothat no sludge is recycled in the system. The controller may beconfigured to adjust carbon concentration (by changing the influent flowrate) to the carbon degradation potential of the bacteria as measured,e.g. by DO.

The measured parameters may include flow rate, (Dissolved Oxygen) DO,(Oxygen Uptake Rate) OUR, pH, temperature, nutrients, contaminationlevel, turbidity and conductivity. A retention time of the bacteria inthe chemostat may be 5-50 hours. The system may further include analert.

The system may include an automatic starting system for starting systemoperation. The automatic starting system may be configured to restart asystem operation by building a first biomass in the chemostat andoperating the chemostat in a continuous flow mode following the buildingof the first biomass.

The system may be configured to test water discharged from the cleanwater output. The system may further include a gravity separation deviceconnected between the wastewater input and the chemostat, for performinga pre-treatment step of oil-water separation. The system may furtherinclude a chemical/mechanical separation unit connected between thewastewater input and the chemostat. The system may further include achemical/mechanical separation unit connected between the gravityseparation device and the chemostat.

The system may further include a first continuous flow chemostat and asecond continuous flow chemostat downstream the first chemostat. Thefirst and the second chemostats may operate at different flow rates.

Another embodiment is a method of treating wastewater. The method mayinclude continuously flowing wastewater into a chemostat andcontinuously discharging clean water out of the chemostat, on-linemeasuring ambient parameters in the chemostat, and adjusting operatingconditions in the chemostat accordingly. The operating conditions areadjusted to maintain a low enough concentration of bacteria within thechemostat to be discharged to the nature without further treatment.

Yet another embodiment is a wastewater treatment system. The systemincludes a wastewater input, a bacteria and nutrients input, an oxygeninput, and a clean water output. The system is configured to maintainthe TSS (total suspended solids) in the bio-reactor lower than the TSSin the wastewater input. Another embodiment is a wastewater treatmentsystem including a chemostat including a wastewater input, a clean wateroutput, a bacteria input, a nutrients input, an oxygen input and sensorsfor measuring ambient parameters. The system also includes an electroniccontroller connected with the sensors, the controller configured toreceive measurements from the sensors and control the operatingconditions of the chemostat accordingly. The system further includes apost-processor connected with the clean water output, the post-processorconfigured to filter residues out of the discharged water. Thepost-processor may include a membrane.

Another embodiment is a wastewater treatment system including achemostat comprising a wastewater input, a clean water output, abacteria input, a nutrients input, an oxygen input and sensors formeasuring ambient parameters. The system further includes apost-processor connected with the clean water output, the post-processorconfigured to filter residues out of the discharged water.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention and to show how the same maybe carried into effect, reference will now be made, purely by way ofexample, to the accompanying drawings.

FIG. 1 is a flow diagram showing the sequential steps for the treatmentof contaminated water in oil refineries and petrochemical plantsaccording to the prior art;

FIG. 2 is a flow diagram of an “activated sludge” process for wastewatertreatment according to the prior art;

FIG. 3 is a flow diagram of a “membrane bioreactors” (“MBR”) process forwastewater treatment according to the prior art;

FIG. 4 is a graph depicting an example of a bacterial growth cycle;

FIG. 5 illustrates an exemplary stirred bioreactor operated as achemostat, with a continuous inflow (the feed) and outflow (theeffluent);

FIG. 6 illustrates an exemplary wastewater treatment system according toa first embodiment of the invention;

FIG. 7 illustrates an exemplary waste water treatment system accordingto a second embodiment of the invention;

FIG. 8 illustrates an exemplary a wastewater treatment system accordingto a third embodiment of the invention;

FIG. 9 illustrates an exemplary a wastewater treatment system accordingto a fourth embodiment of the invention;

FIG. 10 illustrates an exemplary graph showing TPH flow results at thesame site using a waste water treatment system according to theinvention;

FIG. 11 illustrates an exemplary membrane that may be added to a wastewater treatment system comprising a controller for post processing theeffluent; and

FIG. 12 is illustrates an exemplary membrane that may be added to awaste water treatment system devoid of controller for post processingthe effluent

DETAILED DESCRIPTION OF THE INVENTION

It is to be understood that the invention is not limited in itsapplication to the details of construction and to the arrangements ofthe components set forth in the following description or illustrated inthe drawings. The invention is capable of other embodiments and of beingpracticed and carried out in various ways. Also, it is to be understoodthat the phraseology and terminology employed herein are for the purposeof description and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conception,upon which this disclosure is based, may readily be utilized as a basisfor the designing of other structures, methods and systems for carryingout the several purposes of the invention. It is important, therefore,that the claims be regarded as including such equivalent constructionsinsofar as they do not depart from the spirit and scope of theinvention. For a better understanding of the invention, its operatingadvantages and the specific objects attained by its uses, referenceshould be made to the accompanying drawings and descriptive matter whichillustrate exemplary embodiments of the invention. In order to overcomethe disadvantages of the existing wastewater cleaning processes(“Activated Sludge” and “MBR”), the invention provides a new process,using a combination of three components:

1. Continuous culture reactor, also called a chemostat, where bio-sludgeis not recycled into the reacor;

2. A dedicated control system that follows all parameters in theeffluent inlet and outlet and adjusts the process accordingly;

3. Non-aggregate bacteria culture that maximizes the active surface ofbacteria for bio-degradation.

Chemostat—A chemostat is a bioreactor to which fresh medium iscontinuously added, while culture liquid is continuously removed to keepthe culture volume constant. FIG. 5 is a schematic drawing of a stirredbioreactor operated as a chemostat, with a continuous inflow (the feed)and outflow (the effluent). The inflow is controlled to keep the culturevolume constant.

By changing the rate with which the medium (carbon source) is added tothe chemostat, the growth rate of the microorganism can be easilycontrolled. If carbon concentration in the chemostat is increased thebacterial concentration is increased to a point of steady state. Thus,the carbon concentration determines the bacterial concentration. Forexample:

TPH=147 ppm, bacterial concentration is 1*107 cells/ml.

When TPH increase to 210 ppm, the bacterial concentration is increasedto 2*107 cells/ml.

(TPH—total petroleum hydrocarbons is a portion of the TOC)

The System of the Present Invention is Configured to Adjust CarbonConcentration (by changing the influent flow rate) to the carbondegradation potential of the bacteria as measured, e.g. by DO. Thus, thebacterial concentration can be adjusted to utilize the variable carbonand nitrogen sources efficiently, Avoiding the use of excessconcentration (Overkill—as done in Activated Sludge and MBR) allows theprocess to work at a point where bacterial concentration is high enoughto degrade a given carbon source and low enough to create low turbidityand TSS (Total Suspended Solids).

The TSS measured in the effluent from the chemostat may be less than thetypically required 50 ppm for discharging into nature. The system isconfigured to maintain the TSS (total suspended solids) in thebio-reactor lower than the TSS in the wastewater input. Thanks to thelow concentration of bacterial cells, no aggregates are formed, and eachbacterium acts as a single cell which increases the surface availablefor the process and enables biodegradation at a much higher efficiency.

Working at this point has two advantages:

1) Avoiding entrance to the phase where metabolic activity and viabilityis decreased, thus creating a very efficient carbon/nitrogen degradationprocess. According to one embodiment, the system operates at 5%-10% flow(5% flow means that in a 2 liters reactor 0.1 liters per hour areflowing in and out of the reactor. 10% flow means that in a 2 literreactor 0.2 liters per hour are flowing in and out of the reactor). Thismeans that the retention time of the bacteria in the chemostat may be10-20 hours, during this time the bacteria multiply before they arewashed out in order to keep their concentration in the chemostatconstant.2) Enabling the discharge of treated water back to nature without theadditional steps of sludge sedimentation and/or filtration.

The chemostat according to the invention may operate as a continuousflow reactor without using activated sludge. The chemostat can thus beapplied on site while using available infrastructure with highflexibility for modulation of the process.

Automatically Controlled System

In order to utilize a carbon source (e.g. oil) bacteria also typicallyutilize other nutrients, and a defined range of physical conditions suchas O₂ concentration, temperature, and pH. However, in-let wastewater(e.g. refinery waste water) typically includes variations in the carbonconcentration, temperature, and salinity. Bacteria can adjust graduallyto mild variations but not to extreme ones. The latter leads toinstability, reduction in the treatment efficiency and even to a falland dying of the biological treatment. Therefore, maintaining stabilityis useful for a successful bio-treatment.

A chemostat is a very efficient tool if variations in the in-let of awastewater are done gradually. However, to deal with extreme variations,the system may include a control system that stabilizes the biologicalprocess and enables working under optimized conditions.

FIG. 6 is a schematic drawing of a wastewater treatment system (100)according to a first embodiment of the invention, including a chemostat(130), online sensors (140), an electronic controller (170) runningcontrol software for online analysis of sensor measurements and realtime process modifications. Controller (170) is connected with awastewater inlet pump (105) and nutrients feeder (160) and air/oxygensupply (155).

Wastewater (110) is input into the Bio-reactor (130) that automaticallyand efficiently purifies the water using bio-degradation. Should therebe a change in parameters (temperature, pH, etc.) the Bio-reactor'ssensors (140) communicate (150) with the controller (170) toautomatically stabilize the flow as described above, by controlling theincoming flow rate and/or the nutrients feeding into the chemostatand/or the oxygen level. This ensures that a balanced state iscontinuously maintained. The controller may also communicate an alert,such as alert a cell phone on-line and/or the relevant authorities whenat least one of the measured parameters is out of tolerance. Thevirtually sludge-free purified water (180) can be re used or releasedinto the nature.

The on line sensors (140) are used to measure and feed the control unitinformation on multiple parameters such as TPH, nitrogen, dissolvedoxygen, TOC and temperature (listed in table 1 below), anticipate inletfluctuations in conjunction with the controller that has beenspecifically designed for predefined flow rates and identifycontamination type as well as level of contamination. This is useful inorder to be accurate with important parameters (such as TPH, Ammonia,etc.). A few exemplary sensors may be: BioTecor, a TOC analyzeravailable from Pollution Control Systems Inc, Milford, Ohio, USA,Opti-DO model 2000, a DO sensor available from Insite IG, Slidell, La.,USA and Solitax-t, and a turbidity sensor available from Hach-Lange,Dusseldorf, Germany.

TABLE 1 Measured Parameters Out-let/ (Bio. Parameter to measure In-letTreatment) Flow ✓ DO ✓ OUR ✓ pH ✓ ✓ Temp ✓ ✓ Nutrients (e.g. ammonia) ✓Contamination level (TPH/ ✓ ✓ TOC) Turbidity ✓ ✓ Conductivity ✓ ✓

Measuring these parameters or part thereof may be used to define theconditions in the reactor in real time and allow automatic modificationsin the process (in terms of flow rate, nutrients/additives, temperature,air/oxygen etc.) that will increase its stability and the processefficiency. The controller continuously maintains an optimum processbalance between the flow rate, bacterial growth, additives and organiccompound degradation.

EXAMPLE 1 Flow Control

One of the main problems in wastewater treatment is extreme changes inthe quality of the in-let water. The system of the invention canovercome this problem by adjusting the flow rate in relation to thequality of the in-let water. Measuring multiple parameters linked withthe controller enables the system to distinguish between differentstatuses and respond according automatically. For example, if thecontamination is extremely increased (peak), the on line contaminationlevel analyzer (TPH/TOC) will “report” it to the controller and the flowrate will may be automatically decreased or temporarily switched tobatch mode, namely zero flow if necessary, to allow bacteria to adjustto the new conditions.

Moreover, since oxygen and carbon consumption are coupled, the DO(Dissolved Oxygen) level can also be used as a useful indicator to thecontamination (carbon) level. Decrease in the DO level may result fromincrease in the carbon concentration.

EXAMPLE 2 Nutrients

In order to utilize carbon, bacteria typically utilize inorganicnutrients. Therefore, it is important, on the one hand, that nutrientswill not be a limiting factor. However, on the other hand, there is alimitation on nitrogen/phosphate disposal, so excess of these nutrientsis not desired. By measuring nutrients concentrations on line, (directlyor indirectly, e.g. DO), an automatic nutrients adjustment can be doneaccurately.

EXAMPLE 3 Temperature

If the inlet temperature is measured to be higher than the optimizedtemperature in the chemostat, a decrease in the flow rate may achieve a“dilution effect” of the temperature.

Under certain predefined condition the system may issue alerts and ifnecessary automatically stop its operation (e.g. flow=0) to avoidcatastrophe.

For example, in the current conventional wastewater treatment methods(“activated sludge” and “MBR”), if a bacteriocide (a substance thatkills bacteria) is introduced to the reactor, it leads to process deathand the process has to be restarted from the beginning (time and moneyconsuming).

In a process, integration of the on line DO measurement+contaminationlevel measurement may serve as an alarm in case where a toxic compoundis introduced to the chemostat. In other words, while there is acoupling between the contamination level (measured by TOC/TPH) and theoxygen (measured by DO) consumption, in the presence of toxic materialthe DO is decreased even if the contamination level is not changed.

In addition, there may be a correlation between conductivity and sometoxic salts concentration. For example, if the wastewater contains apeak of zinc, which is accompanied by chloride (its anion), the peak maybe detected by a rise in conductivity. If the on line conductivityanalyzer in the in-let ‘senses’ and ‘reports’ to the control system thatconductivity is increased to a higher ratio than the ‘allowed’, thecontrol system will stop the in-let flow to the system to avoid processdeath. The controller according to the invention can identify conditionsunder which the process may be restarted, e.g. when the biologicalprocess is “dead”, possibly due to some unidentified toxin entering thesystem. In this case, a certain volume, which is automatically refreshedby the system, is used as a starter to build a new biomass. Using thecontrol system, the reactor may be refilled in a fed-batch mode(semi-continuous mode), whereby the chemostat is gradually filled at anautomatically determined rate and the biodegrading process begins. Onlywhen the chemostat has been filled will the continuous process start.This method can enable restoring the process in less than 24 hrs. Thesame may also be used to build the first biomass before the continuousprocess takes place, or if the process was stopped from any reason.Alternatively, the restoring process may be conducted in a batch mode,wherein the biodegrading process only starts once the chemostat has beenfilled and biological conditions have stabilized.

The control system may additionally be used to inspect, on line, thetreated water quality and, if necessary, automatically stop dischargingto the nature. If, despite the aforesaid, the carbon degradation isinefficient, it is possible that the contamination source was changedand new bacteria needs to be enriched, e.g. Acinetobacter or Bacillusfor degrading alkanes, Pseudomonas or Sphingomonas for degradingaromatic hydrocarbons and phenols. The system can identify thisoccurrence, e.g. by verifying that the multiple parameters are withinthe normal ranges yet no carbon utilization occurs, and new bacterialenrichment may be suggested. This can be a periodical service (based onthe control system alerts) that is given to the customer by the systemprovider.

FIG. 7 is a schematic drawing of a wastewater treatment system (200)according to a second embodiment of the invention. System (200)includes, in addition to the components described in conjunction withsystem (100) of FIG. 6, a gravity separation device (API) (108) forperforming a pre-treatment step of oil-water separation. FIG. 8 is aschematic drawing of a wastewater treatment system (300) according to athird embodiment of the invention. System (300) includes, in addition tothe components described in conjunction with system (200) of FIG. 7, achemical/mechanical separation unit using DAF (Dissolved Air Flotation)or DGF (Dissolved Gas Flotation) which involves mixing of chemicals inorder to create a flocculation process and then using air to float theflocs. This process separates oil as well as other solids and produceswater with small amounts of hydrocarbons.

FIG. 9 is a schematic drawing of a wastewater treatment system (400)according to a fourth embodiment of the invention. System (400)includes, in addition to the components described in conjunction withsystem (100) of FIG. 6, a second chemostat (131), downstream of thefirst chemostat (130). Chemostat (131) similarly includes sensors (141)and is also connected with the controller (170) and to a nutrientsfeeder (161). The two chemostats (130, 131) may be operated at differentflow rates. For example, the first chemostat (130) may be operated at aflow rate of 10%, whereby it holds each drop of wastewater for 10 hoursand the second chemostat (131) may be operated at a flow rate of 5%,whereby it holds each drop of wastewater for 20 hours. Alternatively,the two chemostats (130, 131) may be operated at a similar flow rate.The combination of (1) A simple biological process and (2) A tightlycontrolled automatic process enables the system of the invention to beeconomic and stable for both small and big water volume. Therefore, thewastewater can always be treated close to where it is created and thereis no need to collect and transport it via a network of pipes and pumpstations to a municipal treatment plant (as done today in some cases).

Using the chemostat technology in combination with the control systemenables simple process and negligible maintenance. While ‘ActivatedSludge’ and ‘MBR’ are complicated processes, with multiple steps andhigh maintenance requirements, the process according to the invention issimple and the maintenance requirements are negligible.

Overall cost saving is about 50% of the operating costs and at least $1per m3. These advantages can be used to justify an upgrade of existinghigh capacity systems. Since such systems process millions of cubicmeters per year, every cent savings per cubic meter treated will resultin dramatic operational savings over one year. Additionally the set upcost of the system according to the invention is relatively low (between1 and three million Dollars, depending on existing infrastructure andcapacity Vs. over 10 Million Dollars for similar systems). Thecalculated ROI (Return On Investment) period may be as short as 18-24months, compared to the ROI for the MBR and Activated Sludgetechnologies which is at least 3 times longer because the initialinvestment is double and the operating costs are 30% higher.

The system according to the invention is advantageous for both smallquantities and big quantities facilities.

For the small quantities facilities (e.g. 5-10 m³/hour capacity), thesystem provides a small footprint, i.e. smaller than 1000 m², ascompared to the Activated Sludge systems which require a footprintapproximately 3 times larger. This is achieved by eliminating the DAFpre-treatment and the Clarifier (sludge removal) post-process. Thepre-treatment may be eliminated due to the system's ability tobio-degrade wastewater having higher degrees of contamination ascompared to prior-art systems. An additional advantage of eliminatingthe DAF is that it creates “Black Sludge”. For small quantitiesfacilities, who cannot economically justify the installation of abio-degradation system, the system of the invention may be temporarilyinstalled and operated, to replace the existing practice of transportingthe wastewater to a cleaning facility.

For large quantities facilities, benefits of the system may include theelimination of the post-processing, sludge removal process and theshortened ROI period. Table 2 below shows results for an oil storagefarm operating in Israel for over one year. The farm releases thetreated water into sand near the seashore with the full authorization ofthe EPA. In embodiments, the system may be configured to at leastachieve one or more of the discharge requirements or less. Otherembodiments may be configured to achieve one or more of the aftertreatment results.

TABLE 2 Operational results Parameter Before Discharge (ppm) TreatmentAfter Treatment Requirements TPH 25-75  1-2 3 COD N/A N/A N/A BOD300-1500 20-30 30 TOC 400-1000 25-50 50 TSS 10-100  2-15 50 Turbidity200-1000 2-7 30 pH 7-9  7-9 6.5-9 Detergents 1-5  1-2 3 Sulfide 50-200<0.1  0.2 Phenol 5   <0.02 0.1 PAH N/A N/A N/A Cresol 1   <0.02 0.15Benzene 0.5 <0.05 0.1 Xylene 0.5 <0.05 0.1 Toluene 0.5 <0.05 0.15

FIG. 10 is a graph showing TPH flow results at the same site using asystem according to the invention with 20% continuous flow.

In another embodiment of the invention, as depicted in FIG. 11, amembrane (185) may be added to the system (500) for post processing theeffluent, which may be useful in cases where a better effluent qualityis required. Alternatively, any other type of post-processing, e.g.settler, sand-filtration, disinfection, or a combination thereof mayreplace the membrane (185).

FIG. 12 depicts yet another embodiment of the invention. System (600)according to this embodiment is devoid of controller. The chemostat(130) operates in continuous flow mode, as explained above, maintaininglow bacterium concentration. This embodiment may be especiallyattractive to facilities having stable inflow. However, if small peaksin the influent composition occur (e.g. carbon, ammonia, temperature),they may be handled by the membrane (185). Alternatively, any other typeof post-processing, e.g. settler, sand-fixation, disinfection, or acombination thereof may replace the membrane (185).

This application discloses several numerical ranges in the text andfigures. The numerical ranges disclosed inherently support any range orvalue within the disclosed numerical ranges even though a precise rangelimitation is not stated verbatim in the specification because thisinvention can be practiced throughout the disclosed numerical ranges.

The above description is presented to enable a person skilled in the artto make and use the invention, and is provided in the context of aparticular application and its requirements. Various modifications tothe preferred embodiments will be readily apparent to those skilled inthe art, and the generic principles defined herein may be applied toother embodiments and applications without departing from the spirit andscope of the invention. Thus, this invention is not intended to belimited to the embodiments shown, but is to be accorded the widest scopeconsistent with the principles and features disclosed herein. Finally,the entire disclosure of the patents and publications referred in thisapplication are hereby incorporated herein by reference.

1. A wastewater treatment system comprising: a continuous flow chemostatcomprising wastewater input, clean water output, bacteria input,nutrients input, oxygen input and one or more sensors configured tomeasure one or more ambient parameters, an electronic controllerassociated with the one or more sensors, the controller configured toreceive measurements from the one or more sensors and control operatingconditions of the chemostat, wherein the electronic controller isconfigured to maintain a sufficiently low concentration of bacteriawithin the chemostat to be discharged to the nature without furthertreatment; and an automatic starting system configured to start systemoperation.
 2. The system of claim 1, wherein the controller isconfigured to control at least one of the waste water input, thenutrients input, and the oxygen input.
 3. The system of claim 1, whereinno sludge is recycled in the system.
 4. The system of claim 1, whereinthe controller is configured to adjust carbon concentration to thecarbon degradation potential of the bacteria.
 5. The system of claim 1,wherein the one or more ambient parameters are selected from the groupconsisting of: flow rate, (Dissolved Oxygen) DO, (Oxygen Uptake Rate)OUR, pH, temperature, nutrients, contamination level, turbidity andconductivity.
 6. The system of claim 1, wherein retention time of thebacteria in the chemostat is not greater than 50 hours.
 7. The system ofclaim 1, comprising an alert.
 8. The system of claim 1, wherein theautomatic starting system is configured to restart a system operation.9. The system of claim 1, wherein the automatic starting system isconfigured to build a first biomass in the chemostat and operate thechemostat in a continuous flow mode following the building of the firstbiomass.
 10. The system of claim 1, wherein the system is configured totest water discharged from clean water output.
 11. The system of claim1, comprising a gravity separation device between the wastewater inputand the chemostat, configured to perform a pre-treatment step ofoil-water separation.
 12. The system of claim 1, comprising achemical/mechanical separation unit between the wastewater input and thechemostat.